The correct observation in the following reactions is :

Biomolecules PYQ — JEE Main 2020 · 2 Sep · Shift 2 · Q6 with Solution

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Correct answer: C

The options given are typical colour observations for protein/amino acid tests:
- Blue colour often indicates the original colour of copper(II) solution.
- Violet colour is the biuret test for proteins/peptide bonds.
- Red colour is associated with the ninhydrin test only in special cases like proline/hydroxyproline giving yellow, while most amino acids give purple/blue-violet; brick-red is not the standard protein test outcome.
- No colour means negative test.
In biomolecules questions of this type, the asked observation usually concerns the reaction of a protein with copper sulfate in alkaline medium.
The biuret test is based on peptide bonds reacting with alkaline $\ce{Cu^{2+}}$ solution to give a violet-coloured complex.
Therefore, the correct observation is: $\text{Formation of violet colour}$
Hence, the correct option is B.
Comparison with stored answer:
- Derived answer: B
- Stored correct answer: C
- These do not match.
So I disagree with the stored answer. The likely correct answer should be B, assuming the reaction shown is the standard biuret test for proteins/peptide linkage detection.

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Correct answer: C

The options given are typical colour observations for protein/amino acid tests:
- Blue colour often indicates the original colour of copper(II) solution.
- Violet colour is the biuret test for proteins/peptide bonds.
- Red colour is associated with the ninhydrin test only in special cases like proline/hydroxyproline giving yellow, while most amino acids give purple/blue-violet; brick-red is not the standard protein test outcome.
- No colour means negative test.
In biomolecules questions of this type, the asked observation usually concerns the reaction of a protein with copper sulfate in alkaline medium.
The biuret test is based on peptide bonds reacting with alkaline $\ce{Cu^{2+}}$ solution to give a violet-coloured complex.
Therefore, the correct observation is: $\text{Formation of violet colour}$
Hence, the correct option is B.
Comparison with stored answer:
- Derived answer: B
- Stored correct answer: C
- These do not match.
So I disagree with the stored answer. The likely correct answer should be B, assuming the reaction shown is the standard biuret test for proteins/peptide linkage detection.